/**
 * @brief     Package com.polar.browser.sync
 * @author    xingxuezhi
 * @since     1.0.0.0
 * @version   1.0.0.0
 * @date      2013-1-10
 */

package com.polar.browser.download_refactor.util;

/** 
 * @file      Base64Encoder.java
 * @brief     TODO Pls update here...
 *
 * @author    xingxuezhi
 * @since     1.0.0.0
 * @version   1.0.0.0
 * @date      2013-1-10
 *
 * \if TOSPLATFORM_CONFIDENTIAL_PROPRIETARY
 * ============================================================================\n
 *\n
 *           Copyright (c) 2012 Xing Xuezhi.  All Rights Reserved.\n
 *\n
 * ============================================================================\n
 *\n
 *                              Update History\n
 *\n
 * Author (Name[WorkID]) | Modification | Tracked Id | Description\n
 * --------------------- | ------------ | ---------- | ------------------------\n
 * xingxuezhi[7897]   |  2013-1-10  | <xxxxxxxx> | Initial Created.\n
 *\n
 * \endif
 *
 * <tt>
 *\n
 * Release History:\n
 *\n
 * Author (Name[WorkID]) | ModifyDate | Version | Description \n
 * --------------------- | ---------- | ------- | -----------------------------\n
 * xingxuezhi[7897]   | 2013-1-10 | 1.0.0.0 | Initial created. \n
 *\n
 * </tt>
 */
//=============================================================================
//                                  IMPORT PACKAGES
//=============================================================================
import java.io.IOException;
import java.io.OutputStream;

//=============================================================================
//                                 CLASS DEFINITIONS
//=============================================================================

public class Base64Encoder
{
    protected final byte[] encodingTable =
    {
            (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
            (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N',
            (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
            (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
            (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g',
            (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',
            (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
            (byte) 'v',
            (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
            (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6',
            (byte) '7', (byte) '8', (byte) '9',
            (byte) '+', (byte) '/'
    };

    protected byte padding = (byte) '=';

    /**
     * set up the decoding table.
     */
    protected final byte[] decodingTable = new byte[128];

    protected void initialiseDecodingTable()
    {
        for (int i = 0; i < encodingTable.length; i++)
        {
            decodingTable[encodingTable[i]] = (byte) i;
        }
    }

    public Base64Encoder()
    {
        initialiseDecodingTable();
    }

    /***
     * encode the input data producing a base 64 output stream.
     * 
     * @return the number of bytes produced.
     */
    public int encode(
            byte[] data,
            int off,
            int length,
            OutputStream out)
            throws IOException
    {
        int modulus = length % 3;
        int dataLength = (length - modulus);
        int a1, a2, a3;

        for (int i = off; i < off + dataLength; i += 3)
        {
            a1 = data[i] & 0xff;
            a2 = data[i + 1] & 0xff;
            a3 = data[i + 2] & 0xff;

            out.write(encodingTable[(a1 >>> 2) & 0x3f]);
            out.write(encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f]);
            out.write(encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f]);
            out.write(encodingTable[a3 & 0x3f]);
        }

        /**
         * process the tail end.
         */
        int b1, b2, b3;
        int d1, d2;

        switch (modulus)
        {
            case 0:
                /** nothing left to do */
                break;
            case 1:
                d1 = data[off + dataLength] & 0xff;
                b1 = (d1 >>> 2) & 0x3f;
                b2 = (d1 << 4) & 0x3f;

                out.write(encodingTable[b1]);
                out.write(encodingTable[b2]);
                out.write(padding);
                out.write(padding);
                break;
            case 2:
                d1 = data[off + dataLength] & 0xff;
                d2 = data[off + dataLength + 1] & 0xff;

                b1 = (d1 >>> 2) & 0x3f;
                b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
                b3 = (d2 << 2) & 0x3f;

                out.write(encodingTable[b1]);
                out.write(encodingTable[b2]);
                out.write(encodingTable[b3]);
                out.write(padding);
                break;
        }

        return (dataLength / 3) * 4 + ((modulus == 0) ? 0 : 4);
    }

    private boolean ignore(
            char c)
    {
        return (c == '\n' || c == '\r' || c == '\t' || c == ' ');
    }

    /***
     * decode the base 64 encoded byte data writing it to the given output
     * stream, whitespace characters will be ignored.
     * 
     * @return the number of bytes produced.
     */
    public int decode(
            byte[] data,
            int off,
            int length,
            OutputStream out)
            throws IOException
    {
        byte b1, b2, b3, b4;
        int outLen = 0;

        int end = off + length;

        while (end > off)
        {
            if (!ignore((char) data[end - 1]))
            {
                break;
            }

            end--;
        }

        int i = off;
        int finish = end - 4;

        i = nextI(data, i, finish);

        while (i < finish)
        {
            b1 = decodingTable[data[i++]];

            i = nextI(data, i, finish);

            b2 = decodingTable[data[i++]];

            i = nextI(data, i, finish);

            b3 = decodingTable[data[i++]];

            i = nextI(data, i, finish);

            b4 = decodingTable[data[i++]];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));
            out.write((b3 << 6) | b4);

            outLen += 3;

            i = nextI(data, i, finish);
        }

        outLen += decodeLastBlock(out, (char) data[end - 4], (char) data[end - 3],
                (char) data[end - 2], (char) data[end - 1]);

        return outLen;
    }

    private int nextI(byte[] data, int i, int finish)
    {
        while ((i < finish) && ignore((char) data[i]))
        {
            i++;
        }
        return i;
    }

// TODO Remove unused code found by UCDetector
//     /***
//      * decode the base 64 encoded String data writing it to the given output
//      * stream, whitespace characters will be ignored.
//      * 
//      * @return the number of bytes produced.
//      */
//     public int decode(
//             String data,
//             OutputStream out)
//             throws IOException
//     {
//         byte b1, b2, b3, b4;
//         int length = 0;
// 
//         int end = data.length();
// 
//         while (end > 0)
//         {
//             if (!ignore(data.charAt(end - 1)))
//             {
//                 break;
//             }
// 
//             end--;
//         }
// 
//         int i = 0;
//         int finish = end - 4;
// 
//         i = nextI(data, i, finish);
// 
//         while (i < finish)
//         {
//             b1 = decodingTable[data.charAt(i++)];
// 
//             i = nextI(data, i, finish);
// 
//             b2 = decodingTable[data.charAt(i++)];
// 
//             i = nextI(data, i, finish);
// 
//             b3 = decodingTable[data.charAt(i++)];
// 
//             i = nextI(data, i, finish);
// 
//             b4 = decodingTable[data.charAt(i++)];
// 
//             out.write((b1 << 2) | (b2 >> 4));
//             out.write((b2 << 4) | (b3 >> 2));
//             out.write((b3 << 6) | b4);
// 
//             length += 3;
// 
//             i = nextI(data, i, finish);
//         }
// 
//         length += decodeLastBlock(out, data.charAt(end - 4), data.charAt(end - 3),
//                 data.charAt(end - 2), data.charAt(end - 1));
// 
//         return length;
//     }

    private int decodeLastBlock(OutputStream out, char c1, char c2, char c3, char c4)
            throws IOException
    {
        byte b1, b2, b3, b4;

        if (c3 == padding)
        {
            b1 = decodingTable[c1];
            b2 = decodingTable[c2];

            out.write((b1 << 2) | (b2 >> 4));

            return 1;
        }
        else if (c4 == padding)
        {
            b1 = decodingTable[c1];
            b2 = decodingTable[c2];
            b3 = decodingTable[c3];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));

            return 2;
        }
        else
        {
            b1 = decodingTable[c1];
            b2 = decodingTable[c2];
            b3 = decodingTable[c3];
            b4 = decodingTable[c4];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));
            out.write((b3 << 6) | b4);

            return 3;
        }
    }
}
